Dual pressure hydraulic apparatus



A. R. BLOOD DUAL. PRESSURE HYDRAULIC APPARATUS sept. s, 1953 Filled slept. '9, 1950 5 Sheets-Sheet l Sept. l8, 1953 A. R. BLOOD DUAL Filed Sept. 9, 1950 PRESSURE HYDRAULIC APPARATUS .5 Sheets-Sheet 2 Sept. 8, 1953 Filed Sept. 9, 1950 A. R. BLOOD DUAL PRESSURE HYDRAULIC APPARATUS y5 Sheets-Sheet 3 Sept. 8, 1953 A. R. BLOOD 2,651,179

DUAL PRESSURE HYDRAULIC APPARATUS 'Filed sep't. 9, 195o 5 sheets-sheet 4 Sept. 8, 1953 A. R. `BLOOD DUAL 4PRESSURE HYDRAULIC APPARATUS '5 Sheets-611%?I 5 Filed Sept. 9, 195o Patented Sept. 8, 1953 DUAL PRESSURE HYDRAULIC Alrsim'rusv Arthur R. Blood, Milwaukee, Wis., assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis.

Application September 9, 1950, Serial No. 183,976

7 claims. l

This invention relates generally to hydraulic apparatus and is more particularly directed to a hydraulic system for use with an engine driven vehicle, hereinafter termed tractor, wherein av single source of pressure fluid is utilized to supply power to a hydraulic motor and, also, to lubricate the vehicle engine.

In tractors having hydraulic power lift apparatus it has been common practice heretofore to equip such tractors with a fluid pressure means which is used solely to operate the power lift, although the source of fluid for such means may also serve to lubricate the transmission or some other part of the tractor. And, where a fluid pressure means is also used to lubricate moving parts of the tractor engine, a second system is installed which is independent of the power lift fluid pressure means. As a result two diierent pumps and drive arrangements therefor mustbe installed on the tractor.

It is, therefore, a primary object of the present invention to provide hydraulic apparatus, for use with a tractor, utilizing a single source of fluid and having a single pumping means wherein fluid is supplied to a hydraulic motor at relatively high pressure and to engine lubricating meansat a relatively low pressure.

Another object of this invention is to provide hydraulic apparatus including a single source of iluid pressure supplying both high and low pressure fluid wherein a single manual control means is operable to direct the ilow of high pressure fluid without appreciably affecting the supply of fluid to the low pressure system.

A'still further object is to provide a hydraulic system having a single source of uid and a single pumping means providing high pressure and low pressure fluid, respectively, to rst and' second devices, and having a manually operable control means communicating with elements of both' of said devices and operable to direct flow to and from the first device while permitting a practically continuous flow to the second device.

Another object of the present invention is to provide a hydraulic system having a single source of fluid and a single pumping means Aproviding high and low pressure fluid, respectively, to 'rst and second devices, a manually operable control means communicating with elements of'both of said devices, and having pressure relief means coacting with said control means to afford a practically continuous ow of low pressure fluid without interfering with the availability ofthe high pressure fluid. y

The construction and operation of apparatus embodying the invention will become more readily apparent as the dis-closure progresses and particularly points out additional objects and advantages of special importance. And accordingly the present invention may be considered as comprising the various constructions, combinations and/or subcombinations of parts as hereinafter more fully set forth in the detailed description and appended claims, reference being had to the accompanying drawings, in which:

Fig. 1 is a plan View of a tractor incorporating apparatus embodying thepresent invention;

Fig. 2 is a side view of the tractor in Fig. 1 with parts broken away and the near driving wheel removed to more clearly show the engine and power lift;

Fig. 3 is an enlarged side view of the engine shown in Figs. 1 and 2 with parts broken away and in section to clarify the relationship of internal structure; I

Fig. 4 is a view taken along line IV-IV of Fig. 3, reduced in scale; Fig. 5 is a side view of Fig. 4; Y Fig. 6 is a section taken along line VI-VI in Fig. 4, with plate 8| shown in surface abutting relation to the outer face of plate 80, and the rear face 11 of engine block 'Il positioned adjacent the inner surface of plate 80;

Fig. 7 is a, section taken along line VII- VII in Fig. 4;

Fig. 8 is a view taken along line VIII-VIII in Fig. 3, reduced in scale Y Fig. 9 is a view taken along line IX-IX in Fig. 3, reduced in scale;

Fig. 10 is a section taken along line XX in Fig. 8;

Fig. 11 is a reduced scale side view of the pump shown in section in Fig. 3;

Fig. 12 is a reduced scale side view of the pump backing plate shown in section in Fig. 3;

Fig. 13 is a schematic illustration of the hydrauli-c lift and lubrication system shown in the preceding gures;

Figs. 14-16 are enlarged sectional views taken along line A-A in Fig. 4, with the control valve in the various positions indicated;

Figs. 17-19 are enlarged sectional views taken along line B-B of Fig. 4 with the valve in lift, hold and lower positions, respectively; and n Figs. 20-22 are enlarged sectional views taken along line C-C of Fig.. 4 with the control valve in lift, hold and lower positions, respectively.

Referring particularly to Figs. 1 and 2 it will be seen that apparatus chosen to illustratethe pres.- ent invention comprises generally a tractor l having a rear axle structure 2 with traction wheels 3 mounted at opposite ends thereof, a rearwardly projecting frame or housing part 5 mounting an engine 6, a forwardly extending frame part 1 mounting an operators seat or station 3 in elevated relation thereto, a pair of upwardly arched frame members la having their rear ends rigidly united with a transverse part I l which in turn is nxedly secured to the forward end of central frame part 1, and a transverse front axle structure I2 secured to forward end portions of frame members I6 and supported on a pair of laterally spaced dirigible front wheels I3.

Rear axle structure 2 includes an enlarged central portion I5 operatively enclosing a differential drive mechanism i6 and a pair of oppositely projecting axle shaft housings I!v each enclosing an axle shaft I8 having its inner end operatively connected with the differential mechanism. The outer or exposed end of each axle shaft terminates in a radially flanged hub portion 26 having fixed thereto, as by bolts 2l, the central disk portion 22 of the driving wheel 3. The forwardly extending tubular frame part 1 encloses a change speed gearing 23 operatively connected with differential mechanism I6 and with the driven element 25 of a clutch 26 which is enclosed in the rearwardly projecting housing 5.

A two cylinder horizontal piston engine is detachably bolted to the rear end of housing 5 and is thereby supported in rearwardly overhanging relation `to central portion i5 of rear axle structure 2, and the adjacent end of the engine crankshaft 21 entering housing 5 has mounted thereon the driving element 28 of clutch 26. Suitable means for controlling the driving uni-t, including brake pedals 36 and 3| and clutch pedal 32, are provided within easy reach of an operator seated at station 8.

The front axle structure I2 comprises a rigid transverse brace member 33 extending between `forward endY portions of frame members i6 with its opposite ends suitably secured in fixed bracing relation to said frame members, and a relatively long bar 35 pivotally connected at its midpoint to the center of brace member 33, as by a bolt 36, with opposite end portions thereof projecting laterally beyond frame members I0. Wheel mounting axle assemblies 31 each include a transverse bar member 38 detachably secured to bar 35, as by bolts 39, for selective adjustment longitudinally thereof to vary the tread spacing of the front wheels. Y

The forward end portions of frame members I are additionally braced by a rigid generally triangular shaped plate member 46 having edge portions thereof suitably fixed, as by welding, to frame members I6. Transverse bar 35 is also braced by a curved rod 4I having its midportion swivel connected with the apex portion of plate member, 46, as by bolt 42, and having opposite end portions xedly connected, as by welding, vvsith the top edge of the outer portions of bar Plate member 56 mounts a steering gear unit 43 operatively connected -to the front wheels through suitable means including telescopically adjustable links 45 and arms 46 and operable through a steering column 41 and steering wheel 48 disposed within easy reach of an operator seated at station 8.

An implement lift mechanism 56 is disposed rearwardly of front axle structure I2 in supported relation to frame members I6. More specifically, a rock shaft I, disposed transversely with remeans such as chain 51, iixed to the free end thereof aifording connection with the underlying beam 56 of a plow 56. Plow beam 58 is pivotally connected at its forward end to a drawbar structure 6I which in turn is suitably attached, as by clamping structure 62, to the tractor front axle structure I2.

The far end of rock shaft 5l, that is the end remote from lift arm 56, has a rock arm 63 nonrotatably fixed thereto in rearwardly extending relation with the free end thereof pivotally connected to a single acting hydraulic ram 65 for actuation thereby. As illustrated, ram 65 is pivotally, detachably secured to the underlying frame member I6, by clamping means 66, and receives iiuid through a hose 61 from an engine driven pump 10.

Looking now at Fig. 3 it will be seen that the engine chosen to illustrate the present invention comprises a main housing or .block 1I with a rst pair of aligned openings (not shown) through opposite end portions thereof supporting bearing structures 12 rotatably mounting a cam shaft 13 therein, and a second pair of aligned openings (also not shown) receiving bearing structures 15 and 16 rotatably supporting opposite ends of crankshaft 21. The major portion of the details of the horizontal piston type engine are not shown since such details are believed unnecessary for a complete understanding of the present invention and their presence in the drawings would only render it more diflicult to visualize and understand the subject invention.

The rear or right hand end portion of the engine, as viewed in Fig. 3, is made up of separable elements aording a housing for the pump structure 16 which is the subject of the present invention. More particularly, the rear face 11 of block 1I has a series of bolt receiving openings 18 (Fig. 9) along the outer edge portion thereof affording means whereby complementary plate structures 86 (see also Fig. 8) and 6l (see also Fig. 4) may be attached in covering relation to the end of the engine block, as by bolts or the like not shown. As seen in Fig. 9, the rear face 11 of the engine block khas a recessed portion 82 extending over nearly the entire surface thereof and a narrow elongated recessed portion 83 at the bottom portion of the face. Recess 83 is a portion of the manifold for engine cooling liquid and, since it comprises no part of this invention, a further explanation thereof is believed unnecessary.. Plate structure S6 is detachably mounted in covering relation to face 11 and includes (see Fig. 8) a circular opening 85, an irregularly shaped elongated recess 36 and a valve housing 81 communicating with recess 86. Plate structure 8l is detachably mounted in covering relation to the lower portion of plate 85 and includes a circular opening 88 therethrough (Fig. 4), .a pair of arcuately shaped recesses 36 and 3| on the inner surface of the plate adjacent opening 88, a bore 92 placing lower recess 96 in communication with an opening in the lower edge of plate 9|, a second bore 93 placing upper recess 9| in communication with an opening in the side edge of plate 8| (see also Fig. 7), and a cylindrical valve housing 95 disposed in overlying parallel relation lto bore 93. Plugs 94 are positioned in the outer ends of bores 92 and 93 after the latter have been formed in plate 8|.

Crankshaft 21 extends rearwardly through plates 80 and 8| and a pulley 96 for driving a fan (not shown) is nonrotatably mounted on the outer end thereof. Intermediate main bearing 16 and an oil seal 91 disposed in opening 88 of plate 8|, crankshaft 21 is splined to drivingly receive element 98 of pump 10 in xed relation thereto. And in this connection it may be noted that pump 1) is of a conventional rotary type having cooperating internal and external rotors 98 and |00, respectively, disposed in coplanar relation with a supporting ring encircling the external rotor (see Fig. 11). ISupporting ring |0| is in turn secured in position in plate 80 between a backing plate |02 (Figs. 3 and l2) and cover plate 8| by suitable means such as bolts |03 extending through aligned openings |05, |06, and |01 in plate |02, ring |0| and cover plate 8|, respectively. Backing plate |02 includes an arcuate recess |08 adapted to be positioned opposite arcuate recess 9| in cover plate 8| to equalize the pressure on the rotors at the dischargeV side of the pump. The action of rotors 98 and |00, upon operation of engine 6, pumps lubricant from sump H8 through passages ||5, ||6 and 92 into arcuate recess 90 from which it is discharged under increased pressure in arcuate recess 9| into supply passage 93. Such a pump mechanism is described in the Hill Patent No. 1,682,563, issued August 28, 1928, to which attention is directed for a more complete description.

Having described the pump proper and its relation to the engine crankshaft, a detailed description will now be given of the ow of oil from a main source to the pump and thence to the engine and hydraulic lift means.

The lower portion of engine block 1| comprises a hollow lubricant confining housing or sump ||0 having a removable cover forming the bottom thereof and being detachably secured to the engine block as by cap screws I2 or the like.

An inwardly projecting boss ||3 in the block at the rear end (right hand end in Fig. 3) Vof sump ||0 has a vertical passage ||5 formed therein communicating with the sump or reservoir 0 through an opening |1 at the lower end 0f the passage. The upper end of passage ||5 intersects a horizontal passage ||6 leading through platev 80 into plate structure 8| where it intersects Vertical passage 92 communicating with arcuate recess 90 on the intake side of the pump 10.

Looking particularly at Fig. 4, the arcuate recess 9| on the upper or discharge side of the pump rotors communicates with horizontal supply passage 93 which intersects a vertical passage (Fig. 6) extending between a valve cham--v ber |2| and a connector |22 for coupling a hose 61 or the like thereto to conduct fluid to ram 65 (Fig. 2). The upper portion of passage |20 is intersected by a valve chamber 95 having a cylindrical valve I 23 therein for controlling the flow of fluid to and from the ram. Valve charnber 95 also communicates with a transverse passage |25 extending through plate 80 and opening into recess 82 of the adjacent rear end portion of block 1| from Which it flows through a passage |61 at the lower end of the block into sump V||0. A second transverse passage v.|26 places valve chamber 95 in communication .with the oil gallery or recess 86 (Fig. 8) in plate 80. This irregularly shaped recess or gallery 86 communicates with main bearings 15 and 16 of engine crankshaft 21 through transverse openings |21 and |28, respectively. Opening |28 .communicates with a horizontal passage |30 (Fig.=3) in the end of the engine block which intersects a vertical passage |3| leading to main bearing 16. Opening |21 communicates with a horizontal Dassage |32 extending the length of the side wall of the engine and having communication with a vertical passage |33 leading yto main bearing 15. Also communicating with gallery 86 is a lateral passage or chamber 81, containinga spring biased piston type relief valve |34, affording communication between gallery 86 and recess portion 82 of face 11 of the engine block through passages |35 and |36 upon attainment of a predetermined pressure in gallery 86. A breather hole |31 at the rear of the piston |38 of the pressure relief valve (see also Fig. 10) prevents fluid pressure from building up behind the piston and also affords communication via recess 82 and passage |81 with the crankcase |0.

And, referring to Figs. 4 and 6, the lower end of passage |20 intersects a transversechamber forming valve housing |2| which extends into gallery 86 and bore |39 in plate 80 and includes herein a ball check relief valve |4| controlling communication between passage |20 and gallery 86. Bore |39 is provided to accommodate the inwardly projecting end portion of the spring biasing means |44 of valve |4| and this bo're terminates at theinner edge of plate with the abutting surface of block face 11 providing cover therefor.

.Valve chamber houses control valve |23 which is a rotatable cylindrical valve having a reduced end'portion |40 thereof projecting outwardly from one edge of plate structure 8| and affording means for manual operation of the valve in a manner to be described later. The cylindrical portion of the valve includes a trans'- verse bore |42 (Fig. 6) therethrough, which is positionable to place the upper and lower portions of discharge passage I 20 in communication with 'each other, a flat side portion |43 positionable to'place the lower portion of passage |20 in communication with by-pass passage |26, and a milled slot |45 inclined longitudinally of the valve (see Figs. 14'l6) and positionable to place theupper portion of passage |2 0, and thereby ram 65, in communication with return passage |25. x

The manually operable valve control mechanism |46 comprises a lever arm |41 nonrotatably xed to the projecting shaft portion |40 of control valve |23, a valve actuating rod |48 pivotally secured at one end to the free end of armv |41 and having its other end positioned within easy reach of an operator seated atstation 8 (Fig. 2), and a plate `|50 rotatablyV mountedon the projecting end portion |40 of valve |23 in surface abutting relation to lever arm |41. Lever arm |41 and plate |50 have arcuate slots (Fig. 5) |5| and |52, respectively, of equal radii formed therein which slots are laterally alignable for-movement relative to a stud |53 secured to plate structure 8|. A compression coil spring |55 is positioned on the outer end of shaft |40 with one end thereof engaging stud |53 and the opposite end fixed in a suitable manner to shaft |40. A washer i156 and pin |51 prevent displacement of -the spring relative to shaft |40 and afford means for causing spring |55 to exert pressure on plate |50 thereby maintaining the latter in surface bearing `relation with arm |41. Lever arm |41 also includes-two relatively small portions thereof, |58 and |60; which project outwardly toward plate |50;` Projection |50 is adapted to engage the `lower edge of plate |50 (Fig. 5) and projection |60 is movable upon rotation of arm |41 into .abutting engagement with a screw |6| adjustably. held by plate |50.'

Referring particularly to Fig. 13 which is a schematic illustration of the structure just described, an account of the operation of the hydraulic lift and engine lubrication system will .now be given. Operation of engine 6 to rotate crankshaft 21 causes a rotary movement'of ro- It'ors38 and |00 to thereby draw lubricating fluid from sump through passages ||5, |l6, 32 into the pump inlet represented vby Athe 'arcuate recess '50, and to dischargeit under'pressure through iarcuat'e recess or 'pressure fluid outlet 9| of pump f.10"`intoj supply passage 93. And 'in this connectionfit' should be noted that any suitable pumpving means, such as a gear type pump, might be employed in place of the-rotor pump illustrated lasvstructural features of the latter form no part of the present invention.

Control valve' |23 is connected in pressure fluid mece'iving Yrelation vwith supply passage 93 and "selectively operable to connect supply passage 33 either with a rst passage means, including passage 61, in communication with rst device 65,

or with a second passage means in communication with a second device represented by the engine lubricating system. The second passage means include passages |26, |30, |32 and manifold 86; and relief valve |34 limits pressure buildup in the second passage means while the second passage means is connected by valve |23 in -pressure fluid receiving relation with supply passage 93. Relief valve |34 is adapted to bypass fluid from the second passage means to the sump or fluid source ||0 at a pressure considerably llower than the pressure which pump is adapted toJbuild up in the ram or first device 65 upon -connection of rst passage 61 with supply passage 93 by valve |23.

With control valve |23 in its lift position (Figs. 13, 14, 17 and 20), lever 41 being positioned along Yline X (Fig. 5), all of the fluid in discharge Dassage 93 flows throughpassage |20, bore |42, conynectr|22 and'hose-@Sl into ram V65. Movement of the piston |65 in the ram effects a forward -movement of rock arm 63 and thereby moves lift arm 56 to a raised position with respect to the ground. Upon completion of the stroke of piston `|65 toward the left end of the ram as viewed in Fig. 13, pressure in discharge passage 93 is increased due to the absence of an outlet for the fluid until vit exceeds a predetermined pressure sufficient to unseat the check valve in pressure relief means |4| whereupon the discharged fluid, `.in excess of that suiiicient to maintain the ram Apiston |55 in its extended position, `ows via chamber |2| (Fig. 6) into gallery 86. From galllery 86 the fluid flows through opening |21 and VVpassages |32 and |33 to main bearing 15 at the A.left end of the engine crankshaft, and also vthrough opening |28 and vpassages |30 and |3| to main bearing 16 at the right end of crankshaft 21. After the oil thus delivered to the main bearings h-as traveled to the camshaft bearings and gtherpartsof the engine requiring lubrication (not shown) it is returned to sump H0. Ahdfin order that the pressure of the lubricating uid delivered to the engine may be controlled, a pressure relief means |34 is placed in lpassage 81 communicating with gallery 86 and the oil reservoir H0. Consequently, when the pressure in gallery 86 exceeds the desired amount for properly lubricating the engine, piston |38 (Fig. 10) in relief means |34 moves against the pressure of the spring |66 and allows oil to flow through passages |35 and |36 to the reservoir.

It should be notedfat this point that the control lever arrangement in the illustrated embodiment of the present invention is such that the f' hand controler rod'i43 for actuating lever |41 :must 'be held in the lift position as long as it is Idesired to deliver uid to the ram. In moving l'le'ver |41 from the hold position into lift position (from line Y to line X, Fig'. 5) projection |50 rthereon engages'the lower edge of plate |50 and 'moves thelatter in a clockwiseV direction along `with the lever.l This movement Winds coil spring |55 l'about its supporting shaft |50 thereby biasing shaft |40 and lever |41 to urge them in a counterclockwise direction. Consequently, when lever |41 is released from the control' of the operator, while in its lift position, spring |55forces the level' back to its hold position along line Y wherein the upper end of slot |52 engages pin |53. Further downward movement of lever arm |41 is relative to plate |50.

Should it be desirable to maintain ram piston |t5 in its extended position with the implement raised, lever |521 be released to move to the hold position as described above, wherein bore |52 is moved away from alignment with passage |23 (see also Fig. i8) and fluid is trapped in the ram cylinder. With the valve thus positioned the ilat side portion |43 of control valve |23 is disposed to place the lower portion of passage |20 in communication with opening |26 (Fig. 21) and thereby direct all the discharge fluid to oil gallery from whence it flows through openings |21 and 20 to the engine parts and through valve |34 to the sump as described above.

To effect a return of the fluid in ram 65 to the source and thereby lower implement 00, control lever lfi'i is moved still farther in a 'counterclock- .wise direction with the longitudinal axis of lever |41 lying generally along'line Z (Fig. 5); In this position slot |45 affords communication between the upper portion of passage |23 and passage |25 (Fig. 16) whereupon the oil in the ram may `low through passage |25 into relieved portion --82 of engine block face il and then through openingy |61 (Fig. 9) back to sump H0. Also, pressure fluid being discharged by pump 10 into the lower portion of vpassage |20 ows'along .the flat portion |43 4of valve |23 through opening |20 into oil gallery 85 and thence to the engine parts and lubricant source as previously described.

Thus it is 'seen from the foregoing that lubrica-nt is flowing to the engine parts at all times during operation other than the brief interval When'the full discharge of pump 10 is required to move ram piston |55 to its extended or lift position. In any commercially practical lift apparatus this time of extension of they ram piston is so brief, usually a few seconds, that the interruption in iiow of oil to the engine during such interval will be negligible.

Also, it may be noted in Fig. 5 that movement yof lever |41 to its lower position along line Z is limited by engagement of the upper end of slot |5| with 'stud |53 and when such engagement is complete groove |45 in control valve1r|-23 isin full communication-with the upper portion-of passage |20 to permit a maximum rate of return of iluid from ram. However, shoulditbe desired to slow the rate of return of fluid fromfthe ram a throttling effect can be achieved by moving adjusting screw I6! downward relative to plate |50 so that projection |60 on lever |41 engages vthe bottom of screw IS! before the upper'endof slot has a chance to strike stud |53. Thus the width of inclined slot |45 which may be placed 'in communication with passage |20 is reduced larly, there is illustrated means for supplyingoil from a single pumping device to an engine for lubrication of parts thereof at relatively low pres- 'sure and, also, to a hydraulic ram at a relatively high pressure for lifting implements and the like.

Furthermore, the supply of low pressure :fluid to the engine is not appreciably affected by the delivery of high pressure fluid to the hydraulic ram.

From a` general point of view, it will be noted thatthe control valve |23 is selectively adjustable to a first or lift positionin which a first and a second housing port of said valve communicate with each other while communication between said first and a third housingport and between said ysecond and a fourth housing` port of said valve is prevented. In the illustrated embodiment of theV invention, the mentioned first housingport is afforded by the part of thevpassage which extends downwardly from the bore 95, in Fig. 4, and the second port is afforded by the part of the passage |20 which extends upwardly from the bore 95. The third housing port is afforded, in the illustrated embodiment of the invention, by the bore |23 which communicates with the bore 95, and the fourth housing port is afforded by the bore |25, all as shown in Fig. 4 and as schematically indicated in Fig. 13. It will further be noted that the control valve |23 is adjustable to a second or hold position in which the mentioned first and third ports communicate with each other while communication between the iirst and second ports and between the second and fourth ports is prevented. The valve |23 is further adjustable to a third or lowering position which affords communication between said second and fourth ports and between said first and third ports while communication between said iirst and second ports is prevented. A check valve controlled connection between the manifold or fluid chamber 85 and the reservoir or source of iluid ||0 is represented by the passage including the second relief valve |34.

Although shown and described in connection with an engine lubricating system and an implement lift means, it is not intended to thereby limit the present invention. Other applications within the scope of the appended claims may become readily apparent to those skilled in the art whenever it is desired to operate a plurality of iluid operated motors and/or devices at different pressures.

It is claimed and desired to secure by Letters Patent:

1. Hydraulic apparatus for supplying high pressure iluid and low pressure fluid, respectively, to a hydraulic motor and to an engine lubricating system, said apparatus comprising, a source of fluid, apump having an inlet and a'pressure fluid outlet, a passage placing said pump inlet in communication with said source, a first passage meansplacing said hydraulic-motor into pressure fluid receiving relation with said pump outlet and into fluid delivering relationwithsaid source, a control valve means operatively associated with said rst passage means andselectivelyoperable toplace said hydraulic motor either into fluid pressure receiving communication `with said pump outlet or into iluid delivering relation with said scurcaa fluid chamber having communication with said engine lubricating system, a second passagefmeans placing said fluid chamber in communication with l said source and connecting Aa portion of said first-passage means intermediate said pump outlet and said control valve -means in pressure fluid delivering relation with said fluidchamber, a third passage means placing said control valve means inv communication with said fluid chamber, said control valve beingA constructed Sothat the discharge fluid from said pump outlet flows into said third passage whenever it is not beingdirected to said hydraulic moltor, -a iirst pressure relief valve operatively associ- -ated with said second passage means and responsive t-o the pressure fluid discharged fromsaid pump so as to control the flow-of iiuid to said uid chamber, and a second pressure relief val-veV 0peratively associated with a portion of said second rpassage means in downstream -relation to said `first pressure relief valve and operative to-A control the vflow offfluid from said fluid chamber to said source. n f

2. In combination with an engine and a hydraulic motor, a hydraulic system comprising a Vfluid reservoir, a pumphaving van inlet anda pressure fluid outlet, a passage connecting said pump inlet in fluid receiving relation with said reservoir, a control valve selectively adjustable to a first position in which a first and a second housing port of said valve communicate with each other while communication between said first and a third housing port and between said second and a fourth housing port of said valve is prevented; and to a second position in which said first and third ports communicate with each other, while communication between said first and second ports and between said second and fourth ports is prevented; and to a third position affording communication between said second and fourth ports, and between said first and third ports, while communication between said first and second ports is prevented; a passageway connecting. said pump outlet with said first port of said control valve, a manifold having a port in fluid communication with said third port of said valve, a check valve controlled connection between said passageway and said manifold, operative to admit pressure fluid from said passageway to said manifold, fluid conduit means connecting said manifold in fluid delivering relation with bearing means of said engine, fluid conduit means connecting said second port of said valve with said hydraulic motor, and fluid conduit means connecting said fourth port of said valve with said fluid reservoir.

3. The combination as set forth in claim 2, and further comprising a check valve controlled connection between said manifold and said iluid reservoir, operative to admit pressure fluid from said manifold to said reservoir.

4. Hydraulic apparatus for supplying high and low pressure fluid, respectively, to first and second devices comprising, a source of fluid, a pump having an inlet and a pressure fluid outlet, a passage placing said pump inlet in communication with said source, a supply passage in pressure fluid receiving relation with said pump outlet, control valve means connected in pressure fluid receiving relation with said supply passage and selectively operable to connect said supply passage either with a iirst passage means in communicaton with said rst device or with a second passage means in communication with said second device, and means for limiting pressure build-up in said second passage means while said second passage means is connected by said valve means in pressure fluid receiving relation with said supply passage, said pressure limiting means including a relief valve adapted to bypass fluid from said second passage means to said source at a pressure considerably lower than the pressure which said pump is adapted to build up in said first device upon connection of said first passage means With said supply passage by said valve means.

5. The combination as set forth in claim 4 and further comprising additional means for limiting pressure build-up in said rst device While said first passage means is connected by said valve means in pressure fluid receiving relation with said supply passage.

6. The combination as set forth in claim 5 in which said means for limiting pressure build-up in said first device comprises a relief valve adapted to bypass fluid from said supply passage into said second passage means upon attainment of a pressure in said rst passage means considerably higher than the limit pressure attainable in said second passage means.

7. Hydraulic apparatus for supplying high and low pressure iiuid, respectively, to a hydraulic motor and to an engine lubricating system, said apparatus comprising a source ofiiuid, a pump having an inlet and a pressure fluid outlet, a passage placing said pump inlet in communication with said source, a supply passage in pressure fluid receiving relation with said pump outlet, a iiuid chamber in fluid delivering relation with said lubricating system, control valve means connected in pressure fluid receiving relation with said supply passage and selectively operable to connect said supply passage either with a rst passage means in communication with said hydraulic motor or with a second passage means in communication with said fluid chamber, and means for limiting pressure build-up in said fluid chamber while said second passage means is connected by said valve means in pressure uid receiving relation with said supply passage, said pressure limiting means including a relief valve adapted to bypass fluid from said fluid chamber to said source at a pressure considerably lower than the pressure which said pump is adapted to build up in said hydraulic motor upon connection of said rst passage means with said supply passage by said valve means.

ARTHUR R. BLOOD.

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